Conventionally, a coated tool, in which a surface of the tool body (hereinafter, collectively referred as the tool body) constituted from; tungsten carbide (hereinafter, referred as WC) based cemented carbide; titanium carbonitride (hereinafter, referred as TiCN) based cermet; or cubic boron nitride (hereinafter, referred as cBN) based ultra-high-pressure sintered material, is coated by a Ti—Al based complex nitride layer as a hard coating layer by the physical vapor deposition method, is known. In addition, it is known that such a hard coating layer exhibits excellent wear resistance.
However, several proposals for improving the hard coating layer are made since: the coated tool that the above-mentioned Ti—Al based complex nitride layer coated on has relatively excellent wear resistance; but abnormal abrasion such as chipping and the like is likely to be occurred in usage in the high-speed intermittent cutting condition.
For example, a surface-coated cutting tool, in which a hard coating layer is formed on the surface of the tool body, is disclosed in Patent Literature 1 (Japanese Unexamined Patent Application, First Publication No. 2012-20391 (A)). In the surface-coated cutting tool disclosed in Japanese Unexamined Patent Application, First Publication No. 2012-20391 (A), the hard coating layer is constituted from one or more layers. Then, in the case where T1 and T2 are defined as the thickness of the thinnest part of the hard coating layer in the ridgeline part of the cutting edge and the thickness of the hard coating layer in the location 1 mm apart from the ridgeline of the cutting edge toward the rake face side, respectively, in the cross section dissecting the cutting tool in a specific plane, the relationship of T1<T2 is satisfied. In addition, Da and Db are set in specific parameter ranges, in the case where Da and Db are defined as the distance from the ridgeline of the cutting edge to the point a in the rake face direction and the distance from the ridgeline of the cutting edge to the point b in the flank face direction, respectively, on the surface of the hard coating layer. In addition, the misalignment of the crystal orientations of the crystal grains constituting the hard coating layer is set to 5° or more and less than 10° in the region corresponding to 10% or more of the region E occupying the thick part of 0.1T1 to 0.9T1 from the surface in the hard coating layer from the point a to the point b. By having the configurations explained above, a surface-coated cutting tool having excellent wear resistance and defect resistance is obtained in Japanese Unexamined Patent Application, First Publication No. 2012-20391 (A).
In addition, it is disclosed that excellent defect resistance can be obtained in heavy cutting work by having a specifically-configured hard coating layer in Patent Literature 2 (Japanese Unexamined Patent Application, First Publication No. 2009-56540 (A)). In Japanese Unexamined Patent Application, First Publication No. 2009-56540 (A), the hard coating layer, which is constituted from an Al and Ti complex nitride layer satisfying the composition formula (Al1-xTix)N (x is atomic ratio and in the range of 0.35 to 0.60), is provided on the surface of the tool body. When crystal orientation analysis is performed on the Al and Ti complex nitride layer with EBSD (Electron beam backward scattering diffraction device), the area ratio of crystal grains having the crystal orientation <100> in the range of 0 to 15° relative to the normal line direction of the polished surface of the tool body is 50% or more. In addition, the hard coating layer is constituted by the Al and Ti complex nitride layer showing the crystal alignment, in which the ratio of small angle grain boundaries)(0<θ<15° is 50% or more, when the angle between adjacent crystal grans is measured.
In the coated tool of Japanese Unexamined Patent Application, First Publication No. 2009-56540 (A), depositing TiAlN as the hard coating layer is disclosed. However, setting the Al content ratio to 0.65 or more is not disclosed or suggested.
From this point of view, a method to increase the Al content ratio x to about 0.9 by forming the hard coating layer by the chemical vapor deposition method is proposed.
For example, Patent Literature 3 (Japanese Unexamined Patent Application, First Publication No. 2011-516722 (A)) discloses that a (Ti1-xAlx)N layer having the Al content ratio value x of 0.65 to 0.95 is deposited by performing chemical vapor deposition in the mixed reaction gas of TiCl4; AlCl3; and NH3, in the temperature range of 650° C. to 900° C. The purpose of Japanese Unexamined Patent Application, First Publication No. 2009-56540 (A) is improving the heat insulating effect by coating an extra Al2O3 layer on the above-mentioned (Ti1-xAlx)N layer. Therefore, it is not clear what kind of influence on the cutting performance of the cutting tool can be obtained by forming the (Ti1-xAlx)N layer having the Al content ratio value x increased to the level of 0.65 to 0.95.
In addition, for example, improving the heat resistance and fatigue strength of the coated tool by: coating the inner layer of a TiCN layer or a Al2O3 layer with an outer layer of a (Ti1-xAlx)N layer (x is 0.65 to 0.90 in the atomic ratio), which is in a cubic structure or cubic structure including a hexagonal structure, by the chemical vapor deposition method; and having the outer layer with compressive stress of 100 to 1100 MPa, is proposed in Patent Literature 4 (Japanese Unexamined Patent Application, First Publication No. 2011-513594 (A)).